ARM: OMAP2+: Drop legacy platform data for OMAP4 DSP

The OMAP4 DSP hwmod is used in DT, but the DT node is not
probing any real driver. The DSP device-tree node shall be
updated as per the new OMAP remoteproc bindings with the
underneath MMU device relying on the ti-sysc infrastructure.

Drop the legacy hwmod data for the DSP device along with the
custom ti,hwmods property. They have to be dropped together
since the early platform data init code is based on the custom
ti,hwmods property.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>